Berkeley Internet Name Domain (Bind); Introduction To Dns - Red Hat ENTERPRISE LINUX 3 Reference Manual

Berkeley Internet Name Domain (BIND)

On most modern networks, including the Internet, users locate other computers by name. This frees
users from the daunting task of remembering the numerical network address of network resources.
The most effective way to configure a network to allow such name-based connections is to set up a
Domain Name Service (DNS) or a nameserver, which resolves hostnames on the network to numerical
addresses and vice versa.
This chapter reviews the nameserver included in Red Hat Enterprise Linux, Berkeley Internet Name
Domain (BIND) DNS server, with an emphasis on the structure of its configuration files and how it
may be administered both locally and remotely.
For instructions on configuring BIND using the graphical Domain Name Service Configuration Tool
(
redhat-config-bind
Linux System Administration Guide.
Warning
If using the Domain Name Service Configuration Tool, do not manually edit any BIND configuration
files as all changes will be overwritten the next time the Domain Name Service Configuration Tool
is used.

12.1. Introduction to DNS

When hosts on a network connect to one another via a hostname, also called a fully qualified domain
name (FQDN), DNS is used to associate the names of machines to the IP address for the host.
Use of DNS and FQDNs also has advantages for system administrators, allowing the flexibility to
change the IP address for a host without effecting name-based queries to the machine. Conversely,
administrators can shuffle which machines handle a name-based query.
DNS is normally implemented using centralized servers that are authoritative for some domains and
refer to other DNS servers for other domains.
When a client host requests information from a nameserver, it usually connects to port 53. The name-
server then attempts to resolve the FQDN based on its resolver library, which may contain authoritative
information about the host requested or cached data from an earlier query. If the nameserver does not
already have the answer in its resolver library, it queries other nameservers, called root nameservers,
to determine which nameservers are authoritative for the FQDN in question. Then, with that infor-
mation, it queries the authoritative nameservers to determine the IP address of the requested host. If
performing a reverse lookup, the same procedure is used, except the query is made with an unknown
IP address rather than a name.
12.1.1. Nameserver Zones
On the Internet, the FQDN of a host can be broken down into different sections. These sections
are organized into a hierarchy (much like a tree), with a main trunk, primary branches, secondary
branches, and so forth. Consider the following FQDN:
bob.sales.example.com
), refer to the chapter called BIND Configuration in the Red Hat Enterprise
Chapter 12.